I am not technical about the drainage, but my turf seems to drain extremely fast. Never have water accumulated on my turf and my kids and dogs can play on it after rain without worry about being muddy. If you get on the turf immediately after the rain, even without any water puddles on it, you can still get a bit wet though.

100% permeable backing is a marketing gimmick, not a patented solution. Artificial grass is a multi-layered system that consists of grass blades attached to a coated backing layer. You don't want to compromise the integrity of synthetic turf; turfs with so claimed 100% permeability have terrible turf bond (glue doesn't hold fibers in place), and blades are easily pulled out.

Proper drainage also depends on the base beneath synthetic turf. If you install turf on concrete, can you expect it to drain well?

There are different city regulations for synthetic turf.

For example, Beverly Hills city code requires turf to have permeable backing with a tuft bind strength of at least 8 pounds and a drain rate of at least 30 inches per hour.

In the city of La Palma, California, artificial turf shall be designed to allow water to percolate through the synthetic grass at a minimum drain rate of 30 inches per hour to an adequate drainage system installed underneath the artificial turf to prevent run-off, pooling, and flooding.

San Francisco requires 50% of surfaces in the front yard to be permeable by using porous asphalt, porous concrete, interlocking pavers, bricks, or landscaping. Areas counted towards the landscaping requirement (20% of the required setback area) can also be credited towards the permeability requirement.